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Target detection method and apparatus and image acquisition device

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Title: Target detection method and apparatus and image acquisition device.
Abstract: The present invention provides a target detection method comprising the following steps controlling a modulated light emitting device to emit optical pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the capabilities of reflecting the light pulse signals of the target to be detected and the background are different, controlling an image sensor to acquire images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions, and it successively scans the same image acquisition region once in the first light intensity and in the second light intensity respectively to obtain a first light intensity image and a second light intensity image, and stores them into corresponding locations in a first frame image and a second frame image respectively, distinguishing the target to be detected and the background, using the first frame image and the second frame image. The present invention also provides a target detection apparatus and an image acquisition device. This invention can precisely detect targets, even moving targets, in a strong light background. ...


Browse recent Shenzhen Taishan Online Technology Co., Ltd. patents - Shenzhen, Guangdong, CN
Inventors: Danwei Shi, Kun Zhou
USPTO Applicaton #: #20120106799 - Class: 382103 (USPTO) - 05/03/12 - Class 382 
Image Analysis > Applications >Target Tracking Or Detecting

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The Patent Description & Claims data below is from USPTO Patent Application 20120106799, Target detection method and apparatus and image acquisition device.

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FIELD OF THE INVENTION

The present invention relates to a target detection field, more specifically, to a target detection method and apparatus and used image acquisition device thereof.

BACKGROUND OF THE INVENTION

Target detection technology widely applied in many fields has always been an important research subject in image processing and computer vision. As a front end processing link, the target detection is one key technology and difficult problem. Only the target in a scene is detected timely, a series of processing work in the following such as target tracking and identifying can be implemented smoothly.

Since target detection technology is very susceptible to the external light especially for sunlight, when a target detection apparatus is used outside, the measurement accuracy will be seriously affected with the detected target in the presence of relatively strong background light, especially under the perpendicular incidence of sunlight or strong light. In addition, positional deviation caused by the shaking and movement of the target to be detected would bring about great impact on the detection accuracy during detection.

How to prevent the relatively strong light from interfering the target detection as well as how to reduce the deviation for the target detection during movement have always been a bottleneck problem and technical difficulty to be solved which puzzle and restrict the practicality of target detection system. Right now, great attention has been paid by domestic and foreign experts to it, and thorough and broad studies have been carried out on such subject. In the present invention, solutions are put forward mainly aiming at such two challenges.

In the prior art, there are three kinds of technical solutions to prevent the sunlight interference and the influence of target movement in the target detection technology, all of which are relevant to the present invention.

In a first method, an additional filter clogging plate or a sunlight occlusion device is utilized. A China patent with application number of No. 200820052299 provides a light curtain that can be used under the sunlight outside. The light curtain comprises a microcontroller which is connected with an IR receiver and an IR transmitter respectively. The body of the IR receiver is provided with a dimmer on its front side so as to filter out visible light as well as reserve IR and far IR signals. However, the above mentioned method cannot solve problems by the root and eliminate the influence of moving objects on the target detection. Besides, the filtrating would cause a decrease of the sensitivity as well. As such, the system has to improve the transmitting power to offset the decrease of sensitivity induced by filtering. In addition, the additional filter clogging plate or the occlusion device to the system will lead to an increase in cost and inconvenience in use.

In a second method, it is a target detection method based on background subtraction method. The basic idea for the background subtraction method is as follows: an average of one or several images in the background is selected to be a background image firstly; then take difference between a current frame and the background, and the obtained difference image is processed appropriately; if the obtained pixel number is larger than a certain threshold value, then a target is determined to be in the background. In this way, the target can be extracted precisely. However, such method is susceptible to many factors including illumination in the background and the movement of background object, as such the produced shadow of moving object will considerably influence the detection accuracy.

The third method is a three-frame difference method. A China patent with application number of No. 200610021067 discloses a moving target detection method in infrared image sequence in complex background, which belongs to the technical field of digital image processing. At first, calculation is performed to obtain difference images of a previous frame and a current frame as well as a current frame and a next frame in the infrared image sequence respectively. After that, a respective change detection template is extracted from the two difference images. Subsequently, a union operation is carried out on the two change detection templates, and their intersection is taken as a moving target template. Finally, a connected component labeling is implemented to the moving target template to obtain the moving target. Wherein the extract of the change detection template specifically comprises: extracting an original change detection template by estimating noise parameters for the difference images in a manner of iteration from both ends of a column diagram to its centre; employing a morphologic processing mode including performing an and operation on small structural units after their erosion and dilation and performing a closing operation on large structural units; wherein the noise parameters for the difference images comprise mean values and variances. Although the three-frame difference method can eliminate the target deviation produced during movement effectively and achieve relatively precise moving target detection, it has not resolved the impact of strong light interference on the target detection. Besides, the algorithm is complex in implementation, in which it is needed to carry out a great deal of morphologic processing to the image to reduce noise in the last period.

During the detection for moving target, the sweep time also has great influence on the detection result. In the detection methods as described above and any other detection methods, it usually takes about 15 ms to scan one frame image. However, the moving object may have experienced large replacement in such time period. Thus, the image acquired in this way and the post image processing will have great deviation.

SUMMARY

OF THE INVENTION

The objective of the present invention is to precisely detect a target object in strong light background, reduce the deviation caused by object movement and provide a target detection method and apparatus and used image acquisition device thereof, aiming at the disadvantages that the above systems are high in cost, complex and large in deviation in the prior art.

The technical solution which is utilized to solve the technical problem in the present invention is as follows: dividing an image sensor into a plurality of image acquisition regions, wherein two consecutive scans are performed on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image and a second light intensity image, and distinguishing a target to be detected from a background according to the first light intensity image and the second light intensity image.

A target detection method is provided in the present invention which comprises the following steps:

controlling a modulated light emitting device to emit light pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the first light intensity is not equal to the second light intensity, and the capabilities of reflecting the light pulse signals of the target to be detected and the background are different;

controlling an image sensor to acquire images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions, wherein two consecutive scans are performed on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image and a second light intensity image which are then stored in corresponding locations in a first frame image and a second frame image respectively;

obtaining the first frame image and the second frame image after finishing the scanning for the plurality of image acquisition regions and distinguishing the target to be detected and the background by means of the first frame image and the second frame image.

In the target detection method of the present invention, the plurality of image acquisition regions are arranged continuously and correspond to a positive integral number of pixel lines or pixel rows of the image sensor respectively.

In the target detection method of the present invention, the distinguishing the target to be detected and the background is achieved through a difference image obtained by subtracting the first frame image from the second frame image.

Another target detection method is provided in the present invention, which comprises the following steps:

controlling a modulated light emitting device to emit light pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the first light intensity is not equal to the second light intensity, and the capabilities of reflecting the light pulse signals of the target to be detected and the background are different;

controlling an image sensor to acquire images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions, wherein two consecutive scans are performed on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image, a second light intensity image and a difference image of the first light intensity image and the second light intensity image, and the difference image are then stored in a corresponding location in a frame difference image;

obtaining the frame difference image after finishing the scanning for the plurality of image acquisition regions and distinguishing the target to be detected and the background by means of the frame difference image.

In the another target detection method of the present invention, the plurality of image acquisition regions are arranged continuously and correspond to a positive integral number of pixel lines or pixel rows of the image sensor respectively.

A target detection apparatus is also provided in the present invention, comprising:

a modulated light emitting device, for emitting light pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the first light intensity is not equal to the second light intensity, and the capabilities of reflecting the light pulse signals of the target to be detected and the background are different;

an image sensor, for acquiring images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions; and

a control unit, for controlling the image sensor to perform two consecutive scans on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image and a second light intensity image which are then stored in corresponding locations in a first frame image and a second frame image; obtaining the first frame image and the second frame image after finishing the scanning for the plurality of image acquisition regions and distinguishing the target to be detected and the background by means of the first frame image and the second frame image.

In the target detection apparatus of the present invention, the plurality of image acquisition regions are arranged continuously and correspond to a positive integral number of pixel lines or pixel rows of the image sensor respectively.

In the target detection apparatus of the present invention, the distinguishing the target to be detected and the background is achieved through a difference image obtained by subtracting the first frame image from the second frame image.

Another target detection apparatus is provided in the present invention, comprising:

a modulated light emitting device, for emitting light pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the first light intensity is not equal to the second light intensity, and the capabilities of reflecting the light pulse signals of the target to be detected and the background are different;

an image sensor, for acquiring images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions; and

a control unit, for controlling the image sensor to perform two consecutive scans on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image, a second light intensity image and a difference image of the first light intensity image and the second light intensity image; storing the obtained difference image in a corresponding location in a frame difference image; obtaining the frame difference image after finishing the scanning for the plurality of image acquisition regions and distinguishing the target to be detected and the background by means of the frame difference image.

In the another target detection apparatus of the present invention, the plurality of image acquisition regions are arranged continuously and correspond to a positive integral number of pixel lines or pixel rows of the image sensor respectively.

An image acquisition device is also provided in the present invention, comprising:

a modulated light emitting device, for emitting light pulse signals with a first light intensity and a second light intensity to a target to be detected and a background, wherein the first light intensity is not equal to the second light intensity, and the capabilities of reflecting the light pulse signals of the target to be detected and the background are different;

an image sensor, for acquiring images of the target to be detected and the background, wherein the image sensor comprises a plurality of image acquisition regions; and

a control unit, for controlling the image sensor to perform two consecutive scans on the same image acquisition region respectively in the first light intensity and in the second light intensity to obtain a first light intensity image and a second light intensity image.

In the image acquisition device of the present invention, the control unit is further used for storing the first light intensity image and the second light intensity image in corresponding locations in a first frame image and a second frame image.

In the image acquisition device of the present invention, the control unit is further used for forming a difference image of the first light intensity image and the second light intensity image and storing the difference image into a corresponding location in a frame difference image.

In the image acquisition device of the present invention, the plurality of image acquisition regions are arranged continuously and correspond to a positive integral number of pixel lines or pixel rows of the image sensor respectively.

When implementing the target detection method and apparatus and used image acquisition device thereof in the present invention, the following advantageous effects can be achieved: since the capabilities of reflecting the light pulse signals of the target to be detected and the background are different, the target to be detected can be distinguished from the background very well so as to reduce the influence of strong light on the target to be detected. Meanwhile, a partitioned consecutive scanning mode is employed in the present invention, which ensures the time slot between two scans for every region to be very small. During this time, the displacement deviation of the moving target to be detected is very small, so that a common image sensor can be used for detecting the target or even the moving target precisely. Therefore, in the present invention, there is no need of professional high-speed camera, thus reducing the cost greatly and improving the equipment performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described with reference to the accompanying drawings and embodiments in the following. In the figures:

FIG. 1 is a flowchart for the target detection method according to the first embodiment of the present invention;

FIG. 2 is a flowchart for the target detection method according to the second embodiment of the present invention;

FIG. 3 is a structure diagram for the target detection apparatus or the image acquisition device in the present invention;

FIGS. 4a-b are schematic diagrams for two kinds of partitioned scanning method of the target detection method in the present invention;

FIG. 5 is a schematic diagram for the process of the target detection method in the present invention;

FIGS. 6a-b are contrast diagrams for the target detection results of the present invention and an un-partitioned method.



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stats Patent Info
Application #
US 20120106799 A1
Publish Date
05/03/2012
Document #
13382140
File Date
03/05/2010
USPTO Class
382103
Other USPTO Classes
International Class
06K9/00
Drawings
7



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